This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
There are 2 modes in which piles may be used to form a foundation : - (1) When the soil is soft for a considerable depth; in which case a large area should be covered with piles connected together by framework at the top, and so forming one united body, which would resist settlement chiefly by the friction of the subsoil against the sides of the piles.
(2) When there is a stratum of hard ground below the soft; in which case the piles should be driven into the hard stratum and each pile would act as an independent column bearing a certain proportion of the whole weight, and resisting settlement both by friction and by its own transverse strength. But this does not come within the range of ordinary house-building.